Frequency Modulation (FM) is used to broadcast radio signals in the Very High Frequency (VHF) band from 30-300 MHz. In the United States, FM radio is typically broadcast over FM channels between 88 and 108 MHz. Each FM channel has a center frequency within a guard band of 50, 100, or 200 KHz. The frequency of a given FM signal varies about its center frequency to encode the audio content being broadcast.
Some wireless telephones are equipped with an FM receiver and channel interface to effectively function as a portable FM radio. These wireless telephones can provide voice calling and play FM radio stations. Some wireless telephones are equipped with a wireless data transceiver and internet protocol interface to effectively function as a portable Internet access device. These wireless telephones can provide voice calling and download media from the Internet. If a wireless telephone provides both FM radio and Internet access, then the user may choose to either receive audio over the FM radio or download the audio over the Internet.